Enhanced Performance of a Molecular Photoacoustic Imaging Agent by Encapsulation in Mesoporous Silicon Nanoparticles
 Authors and Affiliations
 Authors and Affiliations
Jinyoung Kang1, Dokyoung Kim2, Junxin Wang1, Yunho Han3, Jonathan M. Zuidema4, Ali Hariri1, Ji-Ho Park3, Jesse V. Jokerst5, and Michael J. Sailor6,*
1Department of Nanoengineering, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA 2Department of Anatomy and Neurobiology, College of Medicine, Center for Converging Humanities, Kyung Hee University 26 Kyungheedae-Ro, Dongdaemun-Gu, Seoul 02447, Republic of Korea 3Department of Bio and Brain Engineering & KAIST Institute for Health Science and Technology, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea 4Department of Chemistry and Biochemistry, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA 5Department of Nanoengineering, Materials Science and Engineering Program, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA 6Department of Chemistry and Biochemistry, Department of Nanoengineering, Department of Bioengineering, Materials Science and Engineering Program, University of California San Diego, La Jolla, CA 92093, USA
J.K. and D.K. contributed equally to this work.
*To whom correspondence may be addressed.
Abstract Photoacoustic (PA) imaging allows visualization of the physiology and pathology of tissues with good spatial resolution and relatively deep tissue penetration. The method converts near-infrared (NIR) laser excitation into thermal expansion, generating pressure transients that are detected with an acoustic transducer. Here, we find that the response of the PA contrast agent indocyanine green (ICG) can be enhanced 17-fold when it is sealed within a rigid nanoparticle. ICG encapsulated in particles composed of porous silicon (pSiNP), porous silica, or calcium silicate all show greater PA contrast relative to equivalent quantities of free ICG, with the pSiNPs showing the strongest enhancement. A liposomal formulation of ICG performs similar to free ICG, suggesting that a rigid host nanostructure is necessary to enhance ICG performance. The improved response of the nanoparticle formulations is attributed to the low thermal conductivity of the porous inorganic hosts and their ability to protect the ICG payload from photolytic and/or thermal degradation. The translational potential of ICG-loaded pSiNPs as photoacoustic probes is demonstrated via imaging of a whole mouse brain.
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